The invention relates to a method for compacting and/or filling of pulverulent materials in inflexible or flexible containers.
Pulverulent materials are filled into flexible or inflexible containers as, for example drums or sacks. Many pulverulent materials, especially pyrogenically produced oxides or mixed oxides of metals and/or metalloids, as, for example, pyrogenically produced silica, have a low bulk density and/or are strongly permeated with air. These properties necessitate large containers for filling and transport, inevitably giving rise to high packing and transportation costs.
Filling equipment for allowing the pulverulent materials to be de-aerated (compacted) simultaneously with the filling is known in the arts. Because of the increased bulk density of the aerated pulverulent materials, smaller containers are required or larger amounts of pulverulent material can be placed in the containers already at hand. The storage space is economized and the transportation costs are reduced.
Examples of the types of filling equipment which are known in the part art are:
The Carter-Vac-Filler-Equipment for filling of pulverulent products into flexible containers, permeable to gas, as, for the example valve sacks, with the help of a completely closed filling chamber; (CARTER-FILLER).
The Gerivac-Continuous-Compressor for compressing pulverulent products before filling them into small packages, pouches, open sacks, or drums (compare Chemische Rundschau 25 (1971), No. 21, page 647).
The known filling method by means of the Carter-Filler has the following disadvantages:
(a) After the filling procedure, high density variations exist within the pulverulent material in the container (density fluctuations around .+-.20%, in reference to the average density .theta. between the pulverulent material in the middle of the container and the pulverulent material at the container wall.
(b) Too high an increase in the container content necessitates too high an increase of the average density of the pulverulent materials, as, for example with pyrogenically produced silica, and results in an overproportional lengthening of the filling time and partially in undesired changes of the industrial use properties of the pulverulent material. Thus, the increase of the average density of pyrogenically produced silica from 60 to 75 g/l (25%), requires a lengthening of the filling time of about 125%.
(c) A higher packing cost proportion is caused by the high container requirements, as, for example valve sacks with high tensile requirements.
(d) The commitment to a narrowly defined sack material, permeable to gas, prohibits, for example the use of a sack or bag material, essentially or completely impermeable to gas, which can prevent the entry of, for example moisture to the pulverulent material.
The known filling method according to the Continuous Compressor has the disadvantage that the pulverulent material is aerated again after the compression on the way to the container. If a specific density is to be achieved in the container, this can only be achieved by over-compaction of the pulverulent material in the compression device. Herein the danger exists that the industrial use properties of the pulverulent material, as, for example the dispersibility, could be changed undesirably.
The problem of the invention consists of obtaining a homogenous material density in the entire container volume as well as an increase of the average material density in the container without an undesired change in the industrial use properties, for example dispersability and thickening efficiency in filling of pulverulent materials, especially pyrogenically produced oxides or oxide mixtures of metals and/or metalloids, for example of pyrogenically produced silica.